David,2" of concrete is plenty. You could even go down to 1-3/8. 1/4" slope is also sufficient. For your mix use 1 part portland cement to 4 parts sand. Add just a little water.The mixture should look and feel much to dry to use. This is correct mix. Dry mix the sand and cement and lightlysprinkle with water. When you can pack it like a snowball, it's ready. Like I said you will think this is useless butif you get it too wet it will be like regular cement and that's not what you want, you want a dry mix. You should install aPVC shower pan liner even though the shower is on the groundfloor. However, the liner should be sloped also towards thedrain, so you should actually have two separate layers ofconcrete, one sloped with the liner and on top of that, one slopedfor the tile base. The dam should be 6", you could get by withless. Just use your own judgement. I tiled my floor 24 hoursafter sloping the dry mix and haven't had any problems. When youapply your mosaic floor tile, use latex modified mortar (Custom brand "Polyblend" for strength. With regular thin-set the tileswill come up. Check out Pasco's link. They have some good info.One last thing. Your drain should be a two-story drain. The holesin the drain will allow any water that enters the liner to be drained.If you don't have weep holes, it will do no good to install a liner otherthan it will hold the water.